Janet Kwasniak's blog on consciousness and the brain

Another look at consciousness

There is an interesting new paper with a proposed model of consciousness (Michael H. Herzog, Thomas Kammer, Frank Scharnowski. Time Slices: What Is the Duration of a Percept?PLOS Biology, 2016; 14 (4): e1002433 DOI: 10.1371/journal.pbio.1002433). It reviews various theories and experiments in the literature on the subject. Their model is similar to how I have viewed consciousness for a few years, but with important and interesting differences.

They view consciousness as non-continuous, like the frames of a movie, which has seemed the only way to look at consciousness that fits the knowledge that we have of what appear to happen in the brain. They are not dealing with the neurology though and give space to reasons why people have resisted discrete frame and clung to continuous consciousness.

Another aspect of their theory that I like to hear is that the heavy lifting of perception is done unconsciously. The final product of the unconscious processing is a ‘frame’ of consciousness. This fits with the notion that there is not a conscious mind in the sense that we think of a mind. There is only the unconscious mind or simply the mind. Consciousness is a presentation, a moment of experience to remember, a global awareness of a percept.

I have in the past thought of a best-fit-scenario end point of perception, the stable point that would end the iterations of a complex analog computation and be the perception on which consciousness is based. The authors talk of Bayesian statistical computations stopping when they reach an ‘attractor’. This seems the same basic idea but more amenable to experimentation and modeling.

“…During the unconscious processing period, the brain collects information to solve the ill-posed problems of vision, for example, using Bayesian priors. The percept is the best explanation in accordance with the priors given the input. … One important question is how the brain “knows” when unconscious processing is complete and can be rendered conscious. We speculate that percepts occur when processing has converged to an attractor state. One possibility is that hitting an attractor state leads to a signal that renders the content conscious, similarly to, for example, broadcasting in the global workspace theory. … Related questions are the role of cognition, volition, and attention in these processes. We speculate that these can strongly bias unconscious processing towards specific attractor states. For example, when viewing ambiguous figures, a verbal hint or shifting attention can bias observers to perceive either one of the possible interpretations, each corresponding to a different attractor state.”

The most interesting idea (to me) is that the conscious precept is not a snap shot in a series of snap shots but a constructed slab or slice of time in a series of slices. The frames are of short duration but represent slices of time rather than moments. The implication is that we do not, in any sense, have a direct experience of the world, but a highly processed and codified one.

“All features become conscious simultaneously, and the percept contains all the feature information derived from the various detectors. Hence, (a green line) is not actually consciously perceived as green during its actual (sensual stimulus) but later when rendered conscious. The same holds true for temporal features. The stimulus is not perceived during the 50 ms when it is presented. The stimulus is even not perceived for a duration of 50 ms. Its duration is just encoded as a “number,” signifying that the duration was 50 ms in the same way that the color is of a specific hue and saturation.”